Counterbalanced stair.



. UNITED v srarns rarENr ornion CHARLES HENRY BURCH AND.WAINWRIG-I-I'LB.GERVAIS, OF CHICAGO, ILLINOIS, ASSIGNORS T0 VARIETY MANUFACTURINGCOMPANY, OF CHICAGO, ILLINOIS, A

CORPORATION or iILLINOIS.

COUNTERBALANCED STAIR.

Specification of Letters Patent.

PatentedApr. 15, 1913;

Application filed June 17, 1912. SerialNo. 704,004.

To all whom 2'15 may concern: 1

Be it known that we, CHARLES HENRY Boson and TAI'NWRIGHT BACOT GnnvAIs,citizens of the United States, and residents of Chicago, inthe county ofCook and State of Illinois, have invented a certainnew and usefulImprovement in Counterbalanced Stairs, of which the following is a full,clear, concise, and exact description,.referonce beinghad to theaccompanyingdrawings, forming a part of this specification.

Our invention relates to counterbalanced stairs such as are associatedwith theplatforms of fire-escapes, at. a convenient distance above theground and its object is to provide an improved. stair wherein theproper relation of the parts is maintained by providing improved meanswhereby distortion or. sagging; of the. parts of the structure, due tounbalanced. strains, is prevented. It a is usual. in the art in theconstruction of Stairways of this kind to mount two. parallel sidebeams.

or stringers upon a suitable pivot rod and to secure suitable treads orsteps between these side beams or stringers. The stair structure thusformed extendslin but one direction from the pivot rod,which pivotrodusually extends from the side of thebuilding, and in order tocounterbalancethe stairway to keep it normally off the ground in ahorizontal position, a bar secured to one of the stringers is extendedbeyond the pivot rod in the opposite direction and is provided with aweight. Since but one of the stringers is thus counter-weighted, andsince theavhole stairway is held up in this manner, it follows thatthere will be a tendency for the uncounterweighted st-ringer to sag. outof parallel alinement with the other stringer. This has been found to bethe case whenever provision against such sagging is not made.

The means for supportingthe uncounter weighted stringer of thecounterbalanced stair of our invention supports the said stringerwithout causing or allowing the stairway to buckle or twist, as hasoften been found to be the case when the braces and other devicesheretofore proposed have been used.

Our invention is illustrated in the accompanying drawings, in which--Figure 1 is a side elevational View of a counter-balanced stairwayembodying our invention; Fig. 2 is a view showingthe arrangement of ourimproved supporting. means underneath the stairway; and F ig; 3

is a cross-sectional view taken on the line 3-3 of. Fig. 1.

At 1 we have shown an ordinary fire-= escape platform. with a shortstationary stairway portion 2 extending downwardly therefrom. At thebottom of this short staw tionary stairway is located the pivot. rod 3which may extend from the side of a build ing with. which thecounterbalanced. stairway is associated, or it may be carried by r anysuitable supporting means; indicated at 4. Upon this pivot rod 3 aremounted the of gravity when the stairway is in itslhoriaontal position.When thestairway. is in its lowered position, however, the ecnter ofgravity is below the pivot rod. Thus when the stairway is lowered itwill. remain in that position. -Whenit is raised to its horizontalposition it will be there held by the counterweight. The stringer 6 doesnot eX- tend rearwardly beyond the pivotrod 3 any considerable"distance.The stringers may be providedavith suitable railings ,9 carried by thesupports 10, and the front. of the. stringers may be supplemented bystruts 11; withthese features, however, our invention has nethingto do.

The stringer 6 consists of two parallel pieces 12, 12, thisarrangen'lent being employed for the purpose of lightness, andbetweenthetwo stringers the treads 13, .13 are secured. The stringer 5 may, ifdesired, be formed of two parallel pieces as is the stringer 6, but wehave found that the metah saved by so doing is not sufficient to repayfor the labor necessary to construct the other. 1

transverse cambered bar bolted to the.

stringers 5 and 6. This bar 15 at its middle and lowest point, carries asaddle 16, as

clearly shown in Fig. 3. A bent supportingbar 17 slotted at one end asshown at 18 ispassed through the saddle 16 and the slotted portionfitted over the pivot rod 3 inside and against the bearing 7, as shown.

The other end of this bent supporting bar is bolted to the stringer 6 atits free end. As is shown by the drawings, the stringer 6 is preventedfrom sagging by the bent bar 17, which is bent in the form of an archand therefore forms a very strong brace for the stringer 6.Thietransverse supporting bar 15 engaging the off-set portion of the bar17, serves to retain the said bar in proper position at all times. Thebent bar 17 may be raised by tightening the nuts 18, 18, there byraising thesaddle 16. This raising of the bent bar-17 serves to exert astrain upon the free end of the stringer 6, thereby serving to supportthe same. An advantage of,

our improved supporting means is thatjthe strain exerted upon the end ofthe stringer,

6 is largely in an upward direction, there-bein-g little if any straintending to cause the stairway to twist or buckle.

a It will be readily seen th at our bent supporting bar 17 may be raisedat-any time byv tightening the nuts 18, 18, thereby exciting anincreased strain upon the, free end of the stringer 6. While we haveshown the member 17 in the form of a T-bar, this being the preferredform, it should be under stood that this bar may be of any suitableconformation without departing from the spirit of our invention. a

While we have shown our invention in the particular embodiments hereindisclosed, we do not, however, limit ourselvesto the exact constructionsshown, but may employ any equivalents that will suggest themselves to:those skilled in the art.

What we claim is: n

1. In a counterbalanced stairway, a pair low the same and engaging saidbent truss bar at substantially its middle point, and

means carried by saidstrut for adjusting the a amount of bend of saidbent truss bar.

2. In a counterbalanced stairway, a pair of stringers-hung upon' a p1votrod, treads carried by said str1ngers, a welght secured to one of saidstringers, a bent supporting bar.

having a bifurcated end fitting over said pivot rod, 'sa'i-d' bentsupporting bar extend.- ing diagonally of the stairway and secured tothe free end of the unweighted stringer to aid in the support ofthesame, and means carried by-the stairway exerting upon said bentsupporting bar a stress tending to straightenthe same, a bifurcated endof said supporting bar being adapted to turn upon said pivot rod as theamount of bend of said supporting bar becomes less.

3. In a stairway, a pair of stringers hung.

upon a pivot rod, means for holding-up the 'free end of. said stairwayapplied to one of said stringers, a bent supporting bar eXE :tendingdiagonally ofsaid stairway, said .bent supporting bar being positivelysecured to the free end of the other one of said stringers and beingpivotally mounted upon said pivot rod, and means carried by saidstairway engaging said bent supporting bar and exerting thereon a stresstending, to straighten the same.

4. Ina stairway, a pair of stringers hung jupon a pivot rod, means forholdingup the {free end of said stairway applied to one of saidstringers, a truss member consisting of an integral bent supporting barextending Zdiagonally of said stairway to aid in the gsupport of theother stringer, and adjustable 1 means carried by the stairway engagingsaid ithereon tending to straighten the same.

iupon a pivot rod, means for holding up the said stringer-s, a trussmember consisting'iof an integral bent supporting bar extendingTcliagonally of said stairway to aid in the 5. In a stairway, a pair ofstringers hung supportof the other stringer, and an ad- I {justablestrut carried by the stairway exertting upon said bent supporting bar astress atending to straighten the same. V

I In witness whereof, we hereunto subscribev %our names, this 13th dayofJune, 1912.

of stringers hung upon a pivot, treads care ried by said stringers, aweight carried by I one of said stringers, a bent truss bar extendingdiagonallyof the stairwayto aid in 1 the support of the other stringer,a strut carried by said stairway and extending be- CHAS. HENRY BURCH.WAINWRIGHT B. oERvAis Witnesses JOHN ERwooD,

WALTER H. BARRY.

Copies of this patent-may be obtained for five cents each, by addressingthe Commissioner of Patents,

